1. Field of the Invention
The present invention pertains to large engine systems, but more specifically to a system and method for supplying auxiliary power to a locomotive engine to permit automatic shutdown of such locomotive engine in all weather conditions.
2. Background of the Invention
Generally, large diesel engines, such as locomotive engines are not shut down during cold weather conditions due to the difficulty in restarting. Diesel engines do not have the benefit of an electric spark to generate combustion and must rely on heat generated by compressing air to ignite fuel in the engine cylinders. In low temperature conditions (ambient temperatures below about 40° F.), two major factors contribute to the difficulty in starting a diesel engine. First, cold ambient air drawn into the engine must be increased in temperature sufficiently to cause combustion. Second, diesel fuel tends to exhibit poor viscous qualities at low temperatures, making engine starting difficult. Furthermore, engine oil that provides lubrication for the engine is most effective within specific temperature limits, generally corresponding to normal operating temperature of the engine. When cold, the engine lube-oil tends to impede engine starting. Moreover, most engines require a large electrical supply, typically provided by a battery, in order to turn over and start the engine. Unfortunately, batteries are also adversely affected by severe cold weather.
In cold weather, large engines are typically idled overnight to avoid the necessity to restart in the morning and to provide heat to the crew space. Locomotives that must operate in extremely cold environmental conditions must be run continuously, at high fuel cost, or, when shutdown, must be drained of engine coolant and provided supplemental electrical service and heaters, also at high cost.
In warm weather, locomotive engines typically idle to provide air conditioning and other services, including lighting, air pressure and electrical appliances. If the locomotive is shut down, solid-state static inverters that transform dc power from the locomotive batteries to useful ac power can provide electrical power for air conditioning and other services. Devices such as inverters are parasitic loads that tend to drain the batteries, which will adversely affect engine reliability. Alternatively, wayside electrical power can be supplied, but it generally does not maintain air conditioning.
Several systems have been designed to maintain warmth in a large diesel engine under low temperature ambient conditions. For example, U.S. Pat. No. 4,424,775 shows an auxiliary engine for maintaining the coolant, lube-oil, and batteries of a primary diesel engine in restarting condition by using the heat of the auxiliary engine exhaust, to keep coolant, lube-oil, and batteries sufficiently warm. U.S. Pat. No. 4,762,170 shows a system for facilitating the restarting of a truck diesel engine in cold weather by maintaining the fuel, coolant, and lube-oil warm through interconnected fluid systems. U.S. Pat. No. 4,711,204 discloses a small diesel engine for providing heat to the coolant of a primary diesel engine in cold weather. The small engine drives a centrifugal pump with restricted flow such that the coolant is heated, and then pumped through the primary cooling lines in reverse flow. In many of such systems, an electrical generator or inverter may be included to maintain a charge for the batteries.
None of them, however, specifically address other problems associated with the idling of a large diesel engine, such as, primary engine wear, wet stacking due to piston ring leakage as a result of idling for long periods of time in cold weather, high fuel and lube-oil consumption, and so forth. No effective alternative to warm weather idling is known to exist.